This invention relates to a carpet and its method of preparation. More particularly, this invention relates to the use of a coating of a polyvinylidene chloride copolymer latex composition to both secure the yarns of the carpet to the backing and to function as an adhesive layer for bonding the carpet to a secondary backing while providing enhanced flame and smoke retardant properties to the carpet.
Most conventional carpets comprise a primary backing with yarn tufts in the form of cut or uncut loops extending upwardly from the backing and forming a pile surface. In tufted carpets, the yarn is inserted into the backing by tufting needles, and to maintain the yarn tufts permanently in place in the backing, an adhesive coating is applied to the rear surface of the primary backing. This coating is typically referred to as a "tuft-lock" coating.
It is fairly common, for example, to apply a latex of a resin such as polyvinyl chloride to the rear of the carpet and to heat the carpet to dry the latex and thereby adhesively bind the pile yarns in the carpet. Exemplary latex tuft-lock coating layers are disclosed in U.S. Pat. No. 3,695,987 to Wistozky et al and U.S. Pat. No. 4,109,039 to McCoy.
The carpet also typially includes a secondary backing bonded to the primary backing. The secondary backing provides extra padding to the carpet, absorbs noise, adds dimensional stability and often functions as a heat insulator. The secondary backing typically either a woven fabric such as jute or a foam sheet, is laminated to the primary backing by an adhesive layer applied to the tuft-lock coated primary backing.
As an alternative to the use of latex tuft-lock coatings, which require a separate drying step, thermoplastic tuft-lock adhesives have been developed which can be applied as a hot melt. Exemplary hot melt adhesive tuft-lock coatings are disclosed in U.S. Pat. Nos. 3,390,035 and 3,676,280 to Sands, U.S. Pat. No. 3,537,946 to Truax et al and No. Re. 31,826 to Machell. However, the practicality of using such hot melt adhesives is restricted by the requirement of expensive and specialized hot melt extruders which are not available in many carpet mills. British Pat. No. 971,958 to Dow Chemical Company discloses using a hot melt thermoplastic olefin polymer as a tuft-lock coating and as an adhesive for simultaneously laminating a secondary backing to the primary backing. However, the same problems and limitations noted above for hot melt coatings still apply.
The polyvinylidene chloride copolymer latex composition of the present invention is advantageously applied to the rear of the primary backing of the carpet and is dried in the conventional manner for application of latex coatings using conventional equipment which is readily available in most carpet mills. The coating provides excellent tuft-lock properties, and in addition, the dried latex coating has excellent thermoplastic adhesive properties which can be activated in a subsequent heating step for bonding the primary backing to a secondary backing. Thus, the present invention eliminates the necessity of first applying a tuft-lock coating and then applying a different adhesive coating to bind the secondary backing, which adds cost and time to making the carpet.